Vinyl chloride resin composition

ABSTRACT

A vinyl chloride resin composition having excellent impact resistance even at a low temperature and good weather resistance is disclosed. Such vinyl chloride resin composition comprises: 
     (A) a vinyl chloride resin, and 
     (B) a compound rubber type graft copolymer 
     wherein one or more vinyl monomers are graft-polymerized onto a compound rubber that has an average particle diameter of 0.08 to 0.6 μm and possesses such a structure that 1 to 10 wt. % of a polyorganosiloxane rubber component and 90 to 99 wt. % of a polyalkyl (meth)acrylate rubber component are entangled in an inseparable fashion, and the total amount of the polyorganosiloxane rubber component and the polyalkyl (meth)acrylate rubber component is 100 wt. %.

This is a continuation-in-part application of an application having Ser.No. 7/299,433, filed Jan. 23, 1989, now U.S. Pat. No. 4,994,522.

The present invention relates to a resin composition excellent in impactresistance, and, more particularly to a vinyl chloride resin compositionexcellent in impact resistance consisting of a vinyl chloride resin anda specific graft copolymer containing a polyorganosiloxane rubber.

Since vinyl chloride resins are inexpensive, and have various excellentchemical properties and physical properties, the production of vinylchloride resins is largest among synthetic resins, and the resins areused in various fields. Since as well known, molded articles made uponly of a vinyl chloride resin have a major defect that the moldedarticles are fragile to impact, many proposals have been made toovercome this defect. The most effective method thereof is one wherein agraft copolymer obtained by graft polymerization of a monomer such asstyrene, acrylonitrile, and methyl methacrylate onto a rubber-likeelastomer (elastic solid) is mixed with a vinyl chloride resin. Inconnection with the method, there are many technical reports and patents(e.g. Japanese Patent Publication Nos. 22339/1981, 26536/1982, and27689/1985). Such a graft copolymer has already been on the market as animpact modifier for vinyl chloride resins, and has contributedconsiderably to enlarge the application of vinyl chloride resinproducts. However, in certain application, viz., in application at lowtemperatures, a composition having a higher impact strength than that ofknown compositions is demanded. Therefore, a modifier having super-highimpact resistance has been a big subject for a long period of time inthe arts, and if it is realized, larger application can be expected.

Taking the above circumstances into consideration, extensive researcheshave been conducted for the purpose of improving the characteristics ofthe vinyl chloride resins, and have found that by blending a compoundrubber type graft copolymer, which is obtained by graft-polymerizing avinyl monomer onto a compound rubber consisting of a polyorganosiloxanerubber component and a polyalkyl (meth)acrylate rubber component, with avinyl chloride resin, a vinyl chloride resin composition havingexcellent impact resistance, particularly impact resistance at lowtemperature, and weather resistance that have not been attained hithertocan be obtained.

The present invention provides a vinyl chloride resin composition,comprising:

(A) a vinyl chloride resin, and

(b) a compound rubber type graft copolymer wherein one or more vinylmonomers are graft-polymerized onto a compound rubber that has such astructure that 1 to 10 wt. %, preferably 3 to 10 wt. % of apolyorganosiloxane rubber component and 90 to 99 wt. %, preferably 90 to97 wt. % of a polyalkyl (meth)acrylate rubber component are entangled inan inseparable fashion, and the total amount of the polyorganosiloxanerubber component and the polyalkyl (meth)acrylate rubber component is100 wt. %.

The vinyl chloride resin (A) used in the present invention includeshomopolymers of vinyl chloride, and copolymers of 80 wt. % or more ofvinyl chloride and up to 20 wt. % of other monomer copolymerizable withvinyl chloride. As copolymerizable other monomers, vinyl acetate,ethylene, acrylates, and vinyl bromide can be mentioned.

The compound rubber type graft copolymer (B) used in the presentinvention refers to a copolymer wherein one or more vinyl monomers aregraft-polymerized onto a compound rubber that has an average particlediameter of 0.08 to 0.6 μm and possesses such a structure that 1 to 10wt. %, preferably 3 to 10 wt. %, more preferably 5 to 10 wt. % of apolyorganosiloxane rubber component and 90 to 99 wt. %, preferably 90 to97 wt. %, more preferably 90 to 95 wt. % of a polyalkyl (meth)acrylaterubber component are entangled in an inseparable fashion, with the totalamount of the polyorganosiloxane rubber component and the polyalkyl(meth)acrylate rubber component being 100 wt. %.

It is impossible to obtain the excellent properties of the resincomposition of the present invention even if either thepolyorganosiloxane rubber component or the polyalkyl (meth)acrylaterubber component, or a simple mixture of the two rubber components isused as the rubber source instead of the above-mentioned compoundrubber. When the polyorganosiloxane rubber component and the polyalkyl(meth)acrylate rubber component are entangled to form a unitarycomposite, it is for the first time possible to obtain a vinyl chlorideresin composition superior in impact resistance, particularly impactresistance at low temperatures, and weather resistance.

If the amount of polyalkyl (meth)acrylate rubber component exceeds 99wt. %, the impact resistance of a molded article of the obtained resincomposition becomes deteriorated. Therefore, the amount of the polyalkyl(meth)acrylate rubber component constituting the compound rubber isrequired to be in the range of from 90 to 99 wt. % (provided that thetotal amount of the two rubber components is 100 wt. %), and preferablyin the range of 90 to 97 wt. % and more preferably in the range of 90 to95 wt. %. The average particle diameter of said compound rubber isrequired to be in the range of from 0.08 to 0.6 μm. If the averageparticle diameter is less than 0.08 μm, the impact resistance of amolded article of the obtained resin composition becomes deteriorated,while if the average particle diameter exceeds 0.6 μm, the impactresistance of a molded article from the obtained resin compositionbecomes deteriorated, and also the surface appearance of the moldedarticle becomes deteriorated. Emulsion polymerization is most suitableto obtain the compound rubber having such an average particle diameter.It is preferred that firstly a latex of the polyorganosiloxane rubber isprepared, and then the rubber particles of the polyorganosiloxane rubberlatex are impregnated with an alkyl (meth)acrylate and the alkyl(meth)acrylate is subjected to polymerization.

The polyorganosiloxane rubber constituting the above compound rubber maybe prepared by emulsion polymerization using an organosiloxane and acrosslinking agent (I) as described hereinafter. At that time, agraftlinking agent (II) may be used additionally.

Examples of the organosiloxane include various types of cyclic siloxanesof at least three-memberd ring, preferably from 3- to 6-memberedcyclosiloxanes. For example, hexamethylcyclotrisiloxane,octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane,dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane,tetramethyltetraphenylcyclotetrasiloxane, andoctaphenylcyclotetrasiloxane can be mentioned, which may be used aloneor in combination as a mixture of two or more different types. Theorganosiloxane is used in an amount of 50 wt. % or over, preferably 70wt. % or over, of the polyorganosiloxane rubber component.

As the crosslinking agent (I), can be used a trifunctional ortetrafunctional silane type crosslinking agent, such astrimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane,tetraethoxysilane, tetra-n-propoxysilane, and tetrabutoxysilane.Particularly, tetrafunctional crosslinking agent are preferable, and ofthese, tetraethoxysilane is especially preferable. The crosslinkingagent is used in an amount of 0.1 to 30 wt. % of the polyorganosiloxanerubber component.

As the graftlinking agent (II), can be used, for example, a compoundcapable of forming a unit represented by the formula: ##STR1##

    CH.sub.2 =CH-SiR.sup.1.sub.n O.sub.(3-n)/2                 (II- 2)

or

    HS --CH.sub.2).sub.p SiR.sub.n O.sub.(3-n)/2               (II- 3)

wherein R¹ is a methyl group, an ethyl group, a propyl group, or aphenyl group, R² is a hydrogen atom, or a methyl group, n is 0, 1, or 2,and p is a number of 1 to 6.

A (meth)acryloyloxysiloxane capable of forming the unit of the formula(II-1) has a high graft efficiency and thus is capable of formingeffective graft chains, and it is advantageous from the viewpoint ofproviding impact resistance. A methacryloyloxysiloxane is particularlypreferable as the compound capable of forming the unit of the formula(II-1). Specific examples of the methacryloyloxysiloxane includeβ-methacryloyloxyethyldimethoxymethylsilane,γ-methacryloyloxypropylmethoxydimethylsilane,γ-methacryloyloxy-propyldimethoxymethylsilane,γ-methacryloyloxypropyl-trimethoxysilane,γ-methacryloyloxypropylethoxy-diethylsilane,γ-methacryloyloxypropyldiethoxymethyl-silane, andδ-methacryloyloxybutyldiethoxymethylsilane. The grafting agent is usedin an amount of 0 to 10 wt. % of the polyorganosiloxane rubbercomponent.

The latex of this polyorganosiloxane rubber component may be produced bya process disclosed, for example, in U.S. Pat. Nos. 2,891,290 and3,294,725. In the present invention, such a latex is preferablyproduced, for example, in such a manner that a solution mixture of theorganosiloxane, the crosslinking agent (I), and, if desired, thegraftlinking agent (II) are subjected to shear-mixing with water bymeans of e.g. a homogenizer in the presence of a sulfonic acid typeemulsifier such as an alkylbenzenesulfonic acid and an alkylsulfonicacid. An alkylbenzenesulfonic acid is preferable since it serves notonly as an emulsifier for the organosiloxane but also as apolymerization initiator. Further, it is preferable to combine a metalsalt of an alkylbenzenesulfonic acid, or a metal salt of analkylsulfonic acid, since such combined use is effective for maintainingthe polymer under a stabilized condition during the graftpolymerization.

Next, the polyalkyl (meth)acrylate rubber component constituting thecompound rubber may desirably be prepared by using an alkyl(meth)acrylate, a crosslinking agent (III) and a graftlinking agent (IV)as described hereinafter.

Examples of the alkyl (meth)acrylate include alkyl acrylates such asmethyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate,and 2-ethylhexyl acrylate, and alkyl methacrylates such as hexylmethacrylate, 2-ethylhexyl methacrylate, and n-lauryl methacrylate, withn-butyl acrylate preferably used.

Examples of the crosslinking agent (III) include ethylene glycoldimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycoldimethacrylate, and 1,4-butylene glycol dimethacrylate.

Examples of the graftlinking agent (IV) include allyl methacrylate,trially cyanurate and triallyl isocyanurate. Allyl methacrylate can beused also as a crosslinking agent.

These crosslinking agents and graftlinking agents may be used alone orin comination as a mixture of two or more different types. The totalamount of such crosslinking agent and graftlinking agent is 0.1 to 20wt. % of the polyalkyl (meth)acrylate rubber component.

The polymerization of the polyalkyl (meth)acrylate rubber component isconducted by adding a monomer mixture of the alkyl (meth)acrylate, thecrosslinking agent and the graftlinking agent into the latex of thepolyorganosiloxane rubber component neutralized by the addition of anaqueous solution of an alkali such as sodium hydroxide, potassiumhydroxide, or sodium carbonate, and impregnating the monomer into thepolyorganosiloxane rubber particles, followed by addition of a usualradical polymerization initiator and heating them to polymerize. As thepolymerization progresses, a crosslinked network of a polyalkyl(meth)acrylate rubber entangled with the crosslinked network of thepolyorganosiloxane rubber will be formed to obtain a latex of a compoundrubber wherein the polyorganosiloxane rubber component and the polyalkyl(meth)acrylate rubber component are entangled in an inseparable fashion.In carrying out the present invention, as the compound rubber, it ispreferable to use a compound rubber wherein the main skeleton of thepolyorganosiloxane rubber component has repeating units ofdimethylsiloxane, and the main skeleton of the polyalkyl (meth)acrylaterubber component has repeating units of n-butyl acrylate.

The compound rubber thus prepared by emulsion polymerization isgraft-copolymeizable with a vinyl monomer. Further, thepolyorganosiloxane rubber component and the polyalkyl (meth)acrylaterubber component are firmly entangled, so that they cannot be separatedby extraction with a usual organic solvent such as acetone or toluene.The gel content of the compound rubber measured by extraction withtoluene at 90° C. for 12 hours is at least 80 wt. %.

The vinyl monomer to be graft-polymerized onto this compound rubber maybe various monomers including an aromatic alkenyl compound such asstyrene, α-methylstyrene, or vinyltoluene; a methacrylate such as methylmethacrylate or 2-ethylhexyl methacrylate; an acrylate such as methylacrylate, ethyl acrylate, or butyl acrylate; and vinyl cyanide compoundsuch as acrylonitrile or methacrylonitrile. These vinyl monomers may beused alone or in combination as a mixture of two or more differenttypes. Of these vinyl monomers, a methacrylate is preferable, withmethyl methacrylate particularly preferable.

The proportions of the compound rubber and the vinyl monomer in thecompound rubber type graft copolymer (B) are preferably such that thecompound rubber is 30 to 95 wt. %, preferably 40 to 90 wt. %, and thevinyl monomer is 5 to 70 wt. %, preferably 10 to 60 wt. %, based on theweight of the graft copolymer (B). If the vinyl monomer is less than 5wt. %, the dispersion of the graft copolymer (B) in the resincomposition is not enough, while if it exceeds 70 wt. %, the effect forthe improvement of the impact strength lowers.

The vinyl monomer is added to a latex of the compound rubber and thenpolymerized in a single step or in multi-steps by a radicalpolymerization technique to obtain a latex of the compound type graftcopolymer (B). The latex thus obtained is poured into hot water in whicha metal salt such as calcium chloride or magnesium sulfate is dissolved,followed by salting out and coagulation to separate and recover thecompound rubber type graft copolymer (B).

It is preferable that, in the vinyl chloride resin composition of thepresent invention, the cotnent of the compound rubber type graftcopolymer (B) in the entire resin composition is in the range of 3 to 40wt. %. If the content of the compound rubber type graft copolymer (B) isless than 3 wt. %, the effect for improvement of impact resistance ofthe vinyl chloride resin is low, while if the content is more than 40wt. %, the impact resistance is good but it is not preferable because itis not economical.

The mixing of the vinyl chloride resin and the compound rubber typegraft copolymer resin is usually carried out by a known kneadingmachine. Examples of such a machine include mixing rolls, calenderrolls, a Banbury mixer, an extruder, a blow molder, and an inflationmolding machine.

The vinyl chloride resin composition of the present invention mayfurther contain, if necessary, a dyestuff, a pigment, a stabilizer, areinforcing material, a filler, a flame retardant, etc.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted by such specific Examples. In theseExamples, "parts" means "parts by weight".

EXAMPLES

The physical properties in Examples and Comparative Examples weremeasured as follows:

Izod impact strength: Izod impact strength was measured according toASTM D 256 using a notched test piece of 1/4" thickness.

Impact retention ratio: Impact retention ratio was measured using anotched test piece of 1/4" thickness according to ASTM D 256 at 23° C.The Izod impact strength of the test piece before the exposure to asunshine weatherometer was assumed 100%, and the ratio of the Izodimpact strength after the exposure to the Izod impact strength beforethe exposure was designated as the retenion ratio.

The difference of the yellow indices before and after the exposure to asunshine weatherometer: The difference of the yellow indices (YI) of thesample before and after the exposure to a sunshine weatherometer weremeasured in accordance with JIS K-7103.

REFERENCE EXAMPLE 1 Production of a Compound Rubber Type Graft Copolymer(S-1)

Two parts of tetraethoxysilane, 0.5 parts ofγ-methacryloyloxypropyldimethoxymethylsilane, and 97.5 parts ofoctamethylcyclotetrasiloxane were mixed to obtain 100 parts of siloxanemixture. Then, 100 parts of the siloxane mixture were added to 200 partsof distilled water having 1 part of sodium dodecylbenzene sulfonate and1 part of dodecylbenzene sulfonic acid dissolved therein. The mixturewas preliminarily stirred at 10,000 rpm by a homomixer and thenemulsified and dispersed by a homogenizer under a pressure of 300 Kg/cm²to obtain an organosiloxane latex. This mixture was transferred to aseparable flask equipped with a condenser and a stirrer, heated at 80°C. for 5 hours under stirring, and then left at 20° C. for 48 hours.Then, this latex was neutralized to pH 7.4 with an aqueous sodiumhydroxide solution to stop the polymerization to obtain apolyorganosiloxane rubber latex 1. The ratio of polymerization of theorganosiloxane was 89.5%, and the average particle diameter of thepolyorganosiloxane rubber was 0.16 μm.

Then, 20 parts of the polyorganosiloxane rubber latex 1 were introducedinto a separable flask equipped with a stirrer, and 150 parts ofdistilled water and 0.25 parts of sodium dodecylbenzene sulfonate wereadded thereto. After flushing with nitrogen, the mixture was heated to50° C., and a mixed solution comprising 77.5 parts of n-butyl acrylate,1.5 parts of allyl methacrylate, and 0.26 parts of tert-butylhydroperoxide was changed, and the mixture was stirred for 30 min toimpregnate the mixed solution into the polyorganosiloxane rubberparticles. Then, a mixed solution comprising 0.002 parts of ferroussulfate, 0.006 parts of disodium ethylenediaminetetraacetate, 0.26 partsof Rongalit and 5 parts of distilled water was charged thereto toinitiate radical polymerization, and the internal temperature wasmaintained at 70° C. for 2 hours to complete the polymerization reactionto obtain a compound rubber latex. A part of this latex was sampled, andthe average particle diameter of the rubber was measured to find to be0.26 μm. This latex was dried to obtain a solid product, which wasextracted with toluene at 90° C. for 12 hours, whereby the gel contentwas measured to find to be 96.3 wt. %. To 250 parts of this compoundrubber latex, a mixed solution comprising 0.06 parts of tert-butylhydroperoxide, and 15 parts of methyl methacrylate was added dropwiseover a period of 15 min, and the mixture was maintained at 70° C. for 4hours to complete the graft polymerization of the methyl methacrylate tothe compound rubber. The ratio of polymerization of the methylmethacrylate was 99.4%. The graft copolymer latex thus obtained wasadded dropwise to 250 parts of hot water containing 1.5 wt. % of calciumchloride and coagulated, and the coagulated product was separated,washed and dried at 75° C. for 16 hours to obtain 97.6 parts of acompound rubber type graft copolymer (hereinafter referred to as S-1) asa dry powder.

REFERENCE EXAMPLE 2 Production of a Compound Rubber Type Graft Copolymer(S-2)

Two parts of tetraethoxysilane, and 98 parts ofoctamethylcyclotetrasiloxane were mixed to obtain 100 parts of a mixedsiloxane. Then, 100 parts of the mixed siloxane were added to 200 partsof distilled water having 1 part of sodium dodecylbenzene sulfonate and1 part of dodecylbenzene sulfonic acid dissolved therein. The mixturewas preliminarily dispersed by a homomixer and then emulsified anddispersed by a homogenizer in the same way as for the production ofgraft copolymer S-1. The dispersed product was then heated to 80° C. for5 hours, cooled, allowed to stand for 48 hours at 20° C., and finallyneutralized to a pH of 6.9 with an aqueous sodium hydroxide solution tostop the polymerization thereby obtaining a polyorganosiloxane rubberlatex 2. The ratio of polymerization of the organosiloxane was 88.9%,and the average particle diameter of the polyorganosiloxane rubber was0.16 μm.

Then 20.2 parts of the polyorganosiloxane rubber latex 2 were introducedinto a separable flask equipped with a condenser and a stirrer, and 150parts of distilled water and 0.25 parts of sodium dodecylbenzenesulfonate were added thereto. After flushing with nitrogen, the mixturewas heated to 50° C., and a mixed solution comprising 77.5 parts ofn-butyl acrylate, 1.5 parts of allyl methacrylate, and 0.26 parts oftert-butyl hydroperoxide was charged, and the mixture was stirred for 30min. Polymerization of the n-butyl acrylate and allyl methacrylate wascarried out in the same way and under the same conditions as for theproduction of graft copolymer S-1 to obtain a compound rubber latex. Theaverage particle diameter of the compound rubber was 0.26 μm, and thegel content of the rubber measured by the toluene extraction method inthe same way as in Reference Example 1 was 94.2 wt. %. A mixture of 15parts of methyl methacrylate and 0.06 parts of tert-butyl hydroperoxidewas added to the compound rubber latex, and the graft polymerization ofthe methyl methacrylate was carried out under the same conditions as forS-1. The graft copolymer latex thus obtained was coagulated, and thecoagulated product was separated, washed and dried in the same way as inReference Example 1 to obtain 97.7 parts of a dry powder of a compoundrubber type graft copolymer (hereinafter referred to as S-2).

REFERENCE EXAMPLE 3 Production of Compound Rubber Type Graft Copolymers(S-3 to S-5)

The polyorganosiloxane rubber latex 1 prepared in the production of thecompound rubber type graft copolymer S-1 was used to produce compoundrubber type graft copolymers under the same conditions as in ReferenceExample 1 except that such amounts of distilled water, n-butyl acrylateand allyl methacrylate as shown in Table 1 below were used to form butylacrylate rubber component.

                  TABLE 1                                                         ______________________________________                                                    Compound rubber latex                                             Component     3           4       5                                           ______________________________________                                        Polyorganosiloxane                                                                          0           5.7     14.2                                        rubber latex 1                                                                (parts)                                                                       Distilled water                                                                             150         150     150                                         (parts)                                                                       Butyl acrylate                                                                              83.3        81.6    79.1                                        (parts)                                                                       Allyl methacrylate                                                                          1.7         1.7     1.7                                         (parts)                                                                       Tert-butyl    0.26        0.26    0.26                                        hydroxide                                                                     (parts)                                                                       Average particle                                                                            0.26        0.30    0.26                                        diameter of com-                                                              pound rubber (μm)                                                          Gel content of                                                                              95.5        97.3    96.6                                        compound rubber                                                               (wt. %)                                                                       ______________________________________                                    

A mixture of 15 parts of methyl methacrylate and 0.06 parts oftert-butyl hydroperoxide was added to each of the compound rubberlatices, then the graft polymerization of methyl methacrylate onto thecompound rubber was carried out under the same conditions as inReference Example 1, and after the completion of the polymerizationreaction, each of the latices thus obtained was coagulated, and thecoagulated product was separated and dried in the same way as inReference Example 1 to obtain dry powders of compound rubber type graftcopolymers (hereinafter referred to as S-3 to S-5, respectively).

REFERENCE EXAMPLE 4 Production of a Graft Copolymer (S-6)

Twenty parts of the polyorganosiloxane rubber latex 1 were weighed andintroduced together with 150 parts of distilled water and 0.25 parts ofsodium dodecylbenzene sulfonate into a separable flask equipped with astirrer. After flushing with nitrogen, the mixture was heated to 50° C.,and a mixed solution comprising 77.5 parts of n-butyl acrylate, 0.26parts of tert-butyl hydroperoxide was charged, and the mixture wasstirred for 30 min. Thereafter, the same polymerization initiator in thesame amount as in Reference Example 1 was added to effect the emulsionpolymerization to obtain a rubber latex. This case was different fromReference Example 1 in that allyl methacrylate was not added. Theaverage particle diameter of the polymer of the rubber latex and the gelcontent of the rubber measured by the toluene extraction method were0.26 μm, and 6.9 wt. %, respectively. To this rubber latex was addeddropwise a mixed solution comprising 15 parts of methyl methacrylate and0.12 parts of tert-butyl hydroperoxide at 70° C. over 15 min.

Thereafter the mixture was kept at 70° C. for 4 hours to effect thegraft polymerization, and after the completion of the polymerizationreaction, coagulation, separation and drying of the rubber were carriedout in the same manner as in Reference Example 1 to obtain a dry powderof a graft copolymer (hereinafter referred to as S-6).

REFERENCE EXAMPLE 5 Production of Graft Copolymers (S-7 and S-8)

A mixed solution comprising 0.05 parts of tert-butyl hydroperoxide, 15parts of styrene and 10 parts of methyl methacrylate was added dropwiseto 265 parts of the compound rubber latex prepared in the production ofthe compound rubber type graft copolymer S-1 over a period of 30 min. at70° C., and the mixture was maintained at 70° C. for 2 hours to completethe graft polymerization of methyl methacrylate to the compound rubber.The graft copolymer latex thus obtained was coagulated, and thecoagulated product was separated, washed and dried in the same way as inReference Example 1 to obtain 93.4 parts of a dry powder of a compoundrubber type graft copolymer (hereinafter referred to as S-7).

Also, a mixed solution comprising 0.1 parts of tert-butyl hydroperoxideand 30 parts of methyl methacrylate was added dropwise to 206 parts ofthe compound rubber latex prepared in the production of the compoundrubber type graft copolymer S-1 over a period of 30 min. at 70° C., andthe mixture was maintained at 70° C. for 2 hours to complete the graftpolymeization of styrene to the compound rubber. The graft copolymerlatex thus obtained was coagulated, and the coagulated product wasseparated, washed and dried in the same way as in Reference Example 1 toobtain 94.4 parts of a dry powder of a compound rubber type graftcopolymer (hereinafter referred to as S-8).

REFERENCE EXAMPLE 6 Production of Graft Copolymer (S-9)

One part of ethyl orthosilicate, 0.75 parts ofγ-methacryloyloxypropyldimethoxymethylsilane and 100 parts ofoctamethylcyclotetrasiloxane (hereinafter referred to as organosiloxane)were mixed to obtain a siloxane mixture. This mixture was added to 300parts of distilled water having 1.0 part of dodecylbenzene sulfonic aciddissolved therein. The mixture was preliminarily stirred by a homomixerand then emulsified by passing a homogenizer twice under a pressure of250 Kg/cm².

This emulsion was transferred to a separable flask equipped with acondenser, an inlet for nitrogen gas and a stirrer, heated at 90° C. for6 hours under stirring to complete polymerization of the organosiloxaneand to obtain a polyorganosiloxane latex. The ratio of polymerization ofthe organosiloxane was 90.3% and the average particle diameter of thepolyorganosiloxane rubber was 0.14 μm.

This latex was neutralized to pH 8 with an aqueous solution of sodiumcarbonate.

To this latex was dissolved 700 parts of distilled water and 1.5 partsof potassium persulfate, and then the latex was transferred to aseparable flask equipped with a bottle for dropping monomers, acondenser, an inlet for nitrogen gas and a stirrer, heated to 75° C.while flushing with nitrogen gas. Then, a monomer mixture of 50 parts ofacrylonitrile and 150 parts of styrene was slowly added to the flaskthrough the dropping bottle.

After finishing the dropping of the monomer mixture, the monomer mixturewas subjected to polymerization reaction for 2 hours at 65° C. tosubstantially complete the polymerization and then the reaction product(latex) was cooled. Average particle diameter of the graft copolymer inthe latex thus obtained was 0.30 μm.

This latex was poured into hot water having 15 parts of hydrated calciumchloride (CaCl₂ ·2H₂ O) to separate the polymer by the salting out.

After sufficiently washed with water, the polymer was dried at 80° C.for 16 hours to obtain a polyorganosiloxane type graft copolymer(hereinafter referred to as S-9).

The ratio of the grafted polymer portion in the whole graft copolymer(S-9) was 93.5% and degree of the grafting was 46.8%. Polymerizationdegree of the grafting monomers was 99.8%.

EXAMPLES 1 TO 4, AND COMPARATIVE EXAMPLES 1 AND 2

A polyvinyl chloride resin having a degree of polymerization of 700(hereinafter referred to as PVC), and compound rubber type graftcopolymer S-1 or S-2 obtained in Reference Example 1 or 2 was mixed inproportions as shown in Table 2. To 100 parts of each of the mixtureswere added 3 parts of dibutyltin maleate, 1 part of butyl stearate, 0.5parts of stearyl alcohol, and 0.2 parts of a lubricant (Lixol G-47"(trade name) manufactured by Henkel KGaA), the mixture was stirred by aHenschel mixer for 10 min, then kneaded by mixing rolls at a temperatureof 165° C. (lower level) for about 3 min and at a temperature of 195° C.(higher level) for about 4 min, and was pressure-molded for 10 min undera pressure of 100 Kg/cm² into a sample piece. From the sample piecesthus prepared, test pieces were formed and the Izod impact strength wasmeasured. The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                               Compound rubber                                                               type graft           Izod impact                                              copolymer    PVC     strength                                                 Type     (parts) (parts) 23° C.                                                                       0° C.                            ______________________________________                                        Example 1                                                                              S-1        10      90    99    20                                    Example 2                                                                              S-1        15      85    174   46                                    Example 3                                                                              S-1        20      80    173   170                                   Example 4                                                                              S-2        15      85    171   165                                   Comparative                                                                            Metablen ®                                                                           10      90    15.6  6.8                                   Example 1                                                                              C-100*                                                               Comparative                                                                            Metablen ®                                                                           10      90    6.4   3.2                                   Example 2                                                                              W-300*                                                               ______________________________________                                         *An impact modifier for vinyl chloride resin manufactured by Mitsubishi       Rayon Co., Ltd.                                                               **An impact modifier for vinyl chloride resin manufactured by Mitsubishi      Rayon Co., Ltd.                                                          

As apparent from the results shown in Table 2, it can be understood thatthe resin compositions according to the present invention were improvedremarkably in their impact resistance at a low temperature.

EXAMPLE 5, AND COMPARATIVE EXAMPLES 3 AND 4

Example 1, and Comparative Examples 1 to 2 were repeated in the same wayexcept that the compound rubber type graft copolymer (S-1) and theimpact modifiers were used in such proportions as shown in Table 3 toprepare 100 parts of each of mixtures, thereby obtaining test pieces.

The obtained test pieces were subjected to a weather resistance testusing a sunshine weatherometer, and the impact retention ratio after theexposure for 500 hours, the yellow indices YI₁ and YI₂ before and afterthe exposure for 1,000 hours were measured to find its difference YI=YI₂-YI₁. The results are shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________           Compound rubber                                                                            Impact retention radio                                                                    Difference YI between yellow                         type graft   after exposure for                                                                        indices before and after                             copolymer PVC                                                                              500 hours by                                                                              exposure for 1,000 hours                             Type   parts                                                                            parts                                                                            sunshine weatherometer                                                                    by weatherometer                              __________________________________________________________________________    Example 5                                                                            S-1    15 85 87          12                                            Comparative                                                                          Metablen ®                                                                       15 85 23          96                                            Example 3                                                                            C-100                                                                  Comparative                                                                          Metablen ®                                                                       15 85 81          21                                            Example 4                                                                            W-300                                                                  __________________________________________________________________________

As apparent from the results shown in Table 3, it can be understood thatthe resin composition according to the present invention exhibitedexcellent performance in the weather resistance test. Although the resincomposition of Comparative Example 4 exhibited good weather resistance,it was not good because it was low in impact resistance at roomtemperature and at a low temperature as apparent from the results ofComparative Example 2.

EXAMPLES 6 AND 7, AND COMPARATIVE EXAMPLE 5

Example 1 was repeated to prepare test pieces except that the compoundrubber type graft copolymers (S-3) to (S-5) obtained in ReferenceExample 3 were used.

The obtained test pieces were used to measure the Izod impact strength.The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                Compound rubber                                                               type graft          Izod impact                                               copolymer  PVC      strength                                                  Type  (parts)  (parts)  23° C.                                                                        0° C.                           ______________________________________                                        Comparative                                                                             S-3     10       90     7.2    4.5                                  Example 5                                                                     Example 6 S-4     10       90     54     12                                   Example 7 S-5     10       90     78     23                                   ______________________________________                                    

As apparent from the results shown in Table 4, it can be understood thatthe resin composition according to the present invention were improvedremarkably in impact resistance at room temperature and at a lowtemperature.

COMPARATIVE EXAMPLE 6

Example 1 was repeated to prepare test pieces except that the graftcopolymer (S-6) obtained in Reference Examples 4 was used.

The obtained test pieces were used to measure the Izod impact strength.The results are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                               Compound rubber type   Izod impact                                            type graft copolymer                                                                         PVC     strength                                               Type    (parts)    (parts) 23° C.                                                                       0° C.                          ______________________________________                                        Comparative                                                                            S-7       10         90    9.4   5.4                                 Example 6                                                                     ______________________________________                                    

As apparent from the results shown in Table 5, it can be understood thatthe impact resistance was poor in the case of the graft copolymer (S-6)wherein (a) allyl methacrylate was not used and (b) a polyorganosiloxanecomponent and a butyl acrylate component were not formed into a compoundrubber was used.

EXAMPLES 8 AND 9

Example 1 was repeated to prepare test pieces except that the compoundrubber type graft copolymer (S-7) or (S-8) prepared in Reference Example5 was used.

The obtained test pieces were used to measure the Izod impact strength.The results are shown in Table 6.

                  TABLE 6                                                         ______________________________________                                               Compound rubber type   Izod impact                                            type graft copolymer                                                                         PVC     strength                                               Type    (parts)    (parts) 23° C.                                                                       0° C.                          ______________________________________                                        Example 8                                                                              S-7       10         90    168   38                                  Example 9                                                                              S-8       10         90    14.3  9.6                                 ______________________________________                                    

As apparent from the results shown in Table 6, it can be understood thatthe resin compositions according to the present invention were improvedin their impact resistance at room temperature and at a low temperature.

EXAMPLE 10, AND COMPARATIVE EXAMPLES 7 AND 8

Example 1 was repeated to prepare test pieces except that the graftcopolymer (S-9) prepared in Reference Example 6 was used.

The obtained test pieces were used to measure the Izod impact strength.The results are shown in Table 7.

                  TABLE 7                                                         ______________________________________                                                (Compound                                                                     rubber type)        Izod impact                                               Graft copolymer                                                                          PVC      strength                                                  Type  (parts)  (parts)  23° C.                                                                       0° C.                            ______________________________________                                        Example 10                                                                              S-1     70       30     171   169                                   Comparative                                                                             S-9     10       90     8.1   5.2                                   Example 7                                                                     Example 8 S-9     70       30     54.2  6.3                                   ______________________________________                                    

As apparent from the results in Table 7, in case the graft siliconecopolymer (S-9) was used, a polyvinyl chloride composition has a lowimpact strength even if it contained a large amount of the graftcopolymer. On the other hand, however, in case the combined rubber typegraft copolymer (S-1) of the present invention was used, a polyvinylchloride composition has a higher impact strength at a room temperatureand also at a low temperature.

We claim:
 1. A vinyl chloride resin composition, comprising:(A) a vinylchloride resin, and (B) a compound rubber graft copolymerwherein one ormore vinyl monomers are graft-polymerized onto a compound rubber thathas an average particle diameter of 0.08 to 0.6 μm and possesses such astructure that 1 to 10 wt. % of a polyorganosiloxane rubber componentand 90 to 99 wt. % of a polyalkyl (meth)acrylate rubber component areentangled in an inseparable fashion, and the total amount of thepolyorganosiloxane rubber component and the polyalkyl (meth)acrylaterubber component is 100 wt. %.
 2. A vinyl chloride resin compositionaccording to claim 1, wherein said compound rubber comprises 3 to 10 wt.% of the polyorganosiloxane rubber component and 90 to 97 wt. % of thepolyalkyl (meth)acrylate rubber component.
 3. A vinyl chloride resincomposition according to claim 2, wherein said compound rubber comprises5 to 10 wt. % of the polyorganosiloxane rubber component and 90 to 95wt. % of the polyalkyl (meth)acrylate rubber component.
 4. A vinylchloride resin composition according to claim 1, wherein said compoundrubber comprises a polyorganosiloxane rubber component obtained byemulsion polymeization of an organosiloxane and a silane crosslinkingagent, and a polyalkyl (meth)acrylate rubber component obtained bypolymerizing a monomer mixture of an alkyl (meth)acrylate, acrosslinking agent and a graftlinking agent after having thepolyorganosiloxane rubber component impregnated with the monomermixture.
 5. A vinyl chloride resin composition according to claim 1,wherein said compound rubber comprises a polyorganosiloxane rubbercomponent obtained by emulsion polymerization of an organosiloxane, asilane crosslinking agent, and a silane graftlinking agent, and apolyalkyl (meth)acrylate rubber component obtained by polymerizing amonomer mixture of an alkyl (meth)acrylate, a crosslinking agent and agraftlinking agent after having the polyorganosiloxane componentimpregnated with the monomer mixture.
 6. A vinyl chloride resincomposition according to claim 1, wherein said main skeleton of thepolyorganosiloxane rubber component has repeating units ofdimethylsiloxane, and the main skeleton of the polyalkyl (meth)acrylaterubber component has repeating units of n-butyl acrylate.
 7. A vinylchloride resin composition according to claim 1, wherein the gel contentof the compound rubber determined by extraction with toluene is higherthan about 80 wt. %.
 8. A vinyl chloride resin composition according toclaim 1, wherein the vinyl monomer is an ester of methacrylic acid.
 9. Avinyl chloride resin composition according to claim 8, wherein the esterof methacrylic acid is methyl methacrylate.
 10. A vinyl chloride resincomposition according to claim 1, wherein the composition comprises 97to 60 wt. %, based on the weight of the composition, of (A) a vinylchloride resin and 3 to 40 wt. %, based on the weight of thecomposition, of (B) a compound rubber graft copolymer.